Method of preparing battery electrodes

ABSTRACT

Provided herein is a method for preparing a battery electrode based on an aqueous slurry. The method disclosed herein has the advantage that an aqueous solvent can be used in the manufacturing process, which can save process time and facilities by avoiding the need to handle or recycle hazardous organic solvents. Therefore, costs are reduced by simplifying the total process. In addition, the batteries having the electrodes prepared by the method disclosed herein show impressive energy retention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of the International Application No.PCT/CN2016/109723, filed Dec. 13, 2016, which claims priority to U.S.Provisional Patent Application No. 62/279,841, filed Jan. 18, 2016, allof which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to lithium-ion batteries in the application ofsustainable energy area. More particularly, this invention relates tothe use of aqueous-based slurries for preparing battery electrodes.

BACKGROUND OF THE INVENTION

Lithium-ion batteries (LIBs) have attracted extensive attention in thepast two decades for a wide range of applications in portable electronicdevices such as cellular phones and laptop computers. Due to rapidmarket development of electric vehicles (EV) and grid energy storage,high-performance, low-cost LIBs are currently offering one of the mostpromising options for large-scale energy storage devices.

In general, a lithium ion battery includes a separator, a cathode and ananode. Currently, electrodes are prepared by dispersing fine powders ofan active battery electrode material, a conductive agent, and a bindermaterial in an appropriate solvent. The dispersion can be coated onto acurrent collector such as a copper or aluminum metal foil, and thendried at an elevated temperature to remove the solvent. Sheets of thecathode and anode are subsequently stacked or rolled with the separatorseparating the cathode and anode to form a battery.

Polyvinylidene fluoride (PVDF) has been the most widely used bindermaterials for both cathode and anode electrodes. Compared to non-PVDFbinder materials, PVDF provides a good electrochemical stability andhigh adhesion to the electrode materials and current collectors.However, PVDF can only dissolve in some specific organic solvents suchas N-Methyl-2-pyrrolidone (NMP) which requires specific handling,production standards and recycling of the organic solvents in anenvironmentally-friendly way. This will incur significant costs in themanufacturing process.

The use of aqueous solutions instead of organic solvents is preferredfor environmental and handling reasons and therefore water-basedslurries have been considered. Water soluble binders such ascarboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) havebeen attempted. However, CMC and SBR are generally limited to anodeapplications.

U.S. Pat. No. 8,956,688 B2 describes a method of making a batteryelectrode. The method comprises measuring the zeta potential of theactive electrode material and the conductive additive material;selecting a cationic or anionic dispersant based on the zeta potential;determining the isoelectric point (IEP) of the active electrode materialand the conductive additive material; dispersing an active electrodematerial and a conductive additive in water with at least one dispersantto create a mixed dispersion; treating a surface of a current collectorto raise the surface energy of the surface to at least the surfacetension of the mixed dispersion; depositing the dispersed activeelectrode material and conductive additive on a current collector; andheating the coated surface to remove water from the coating. However,the method is complicated, involving measurements of the zeta potentialof the active electrode material and the conductive additive material,and isoelectric point (IEP) of the active electrode material and theconductive additive material. Furthermore, an additional surfacetreatment step for treating the surface of the current collector isrequired in order to enhance the capacity retention.

U.S. Pat. No. 8,092,557 B2 describes a method of making an electrode fora rechargeable lithium ion battery using a water-based slurry having apH between 7.0 and 11.7, wherein the electrode includes anelectro-active material, a (polystyrenebutadiene rubber)-poly(acrylonitrile-co-acrylamide) polymer, and a conductive additive.However, this method does not provide any data for evaluating theelectrochemical performance of the electrodes prepared by this method.

U.S. Patent Application No. 2013/0034651 A1 describes a slurry for themanufacture of an electrode, wherein the slurry comprises a combinationof at least three of polyacrylic acid (PAA), carboxymethyl cellulose(CMC), styrene-butadiene rubber (SBR) and polyvinylidene fluoride (PVDF)in an aqueous solution and an electrochemically activateable compound.However, the slurry for preparing the cathode electrode comprisesacetone or other organic solvents such as NMP and DMAC.

In view of the above, there is always a need to develop a method forpreparing cathode and anode electrodes for lithium-ion battery using asimple, inexpensive and environmentally friendly method.

SUMMARY OF THE INVENTION

The aforementioned needs are met by various aspects and embodimentsdisclosed herein.

In one aspect, provided herein is a method of preparing a batteryelectrode, comprising the steps of:

1) pre-treating an active battery electrode material in a first aqueoussolution having a pH from about 2.0 to about 7.5 to form a firstsuspension;

2) drying the first suspension to obtain a pre-treated active batteryelectrode material;

3) dispersing the pre-treated active battery electrode material, aconductive agent, and a binder material in a second aqueous solution toform a slurry;

4) homogenizing the slurry by a homogenizer to obtain a homogenizedslurry;

5) applying the homogenized slurry on a current collector to form acoated film on the current collector; and

6) drying the coated film on the current collector to form the batteryelectrode.

In certain embodiments, the active battery electrode material is acathode material, wherein the cathode material is selected from thegroup consisting of LiCoO₂, LiNiO₂, LiNi_(x)Mn_(y)O₂,Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂, LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅,LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄, LiFeO₂, LiFePO₄, andcombinations thereof, wherein each x is independently from 0.3 to 0.8;each y is independently from 0.1 to 0.45; and each z is independentlyfrom 0 to 0.2.

In some embodiments, the pH of the first aqueous solution is at a rangefrom about 4 to about 7 and the first suspension is stirred for a timeperiod from about 2 minutes to about 12 hours. In further embodiments,the first aqueous solution comprises one or more acids selected from thegroup consisting of H₂SO₄, HNO₃, H₃PO₄, HCOOH, CH₃COOH, H₃C₆H₅O₇,H₂C₂O₄, C₆H₁₂O₇, C₄H₆O₅, and combinations thereof.

In certain embodiments, the first aqueous solution further comprisesethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, or acombination thereof.

In some embodiments, the first suspension is dried by a double-conevacuum dryer, a microwave dryer, or a microwave vacuum dryer.

In certain embodiments, the conductive agent is selected from the groupconsisting of carbon, carbon black, graphite, expanded graphite,graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers,graphitized carbon flake, carbon tubes, carbon nanotubes, activatedcarbon, mesoporous carbon, and combinations thereof.

In some embodiments, the conductive agent is pre-treated in an alkalinesolution or a basic solution for a time period from about 30 minutes toabout 2 hours, wherein the alkaline solution or basic solution comprisesa base selected from the group consisting of H₂O₂, LiOH, NaOH, KOH,NH₃.H₂O, Be(OH)₂, Mg(OH)₂, Ca(OH)₂, Li₂CO₃, Na₂CO₃, NaHCO₃, K₂CO₃,KHCO₃, and combinations thereof.

In certain embodiments, the conductive agent is dispersed in a thirdaqueous solution to form a second suspension prior to step 3).

In some embodiments, the binder material is selected from the groupconsisting of styrene-butadiene rubber (SBR), carboxymethyl cellulose(CMC), polyvinylidene fluoride (PVDF), acrylonitrile copolymer,polyacrylic acid (PAA), polyacrylonitrile, poly(vinylidenefluoride)-hexafluoropropene (PVDF-HFP), latex, a salt of alginic acid,and combinations thereof. In further embodiments, the salt of alginicacid comprises a cation selected from Na, Li, K, Ca, NH₄, Mg, Al, or acombination thereof.

In some embodiments, the binder material is dissolved in a fourthaqueous solution to form a resulting solution prior to step 3).

In certain embodiments, each of the first, second, third and fourthaqueous solutions independently is purified water, pure water,de-ionized water, distilled water, or a combination thereof.

In some embodiments, the slurry or homogenized slurry further comprisesa dispersing agent selected from the group consisting of ethanol,isopropanol, n-propanol, t-butanol, n-butanol, lithium dodecyl sulfate,trimethylhexadecyl ammonium chloride, alcohol ethoxylate, nonylphenolethoxylate, sodium dodecylbenzene sulfonate, sodium stearate, andcombinations thereof.

In certain embodiments, the homogenizer is a stirring mixer, a blender,a mill, an ultrasonicator, a rotor-stator homogenizer, or a highpressure homogenizer.

In some embodiments, the ultrasonicator is a probe-type ultrasonicatoror an ultrasonic flow cell.

In certain embodiments, the ultrasonicator is operated at a powerdensity from about 10 W/L to about 100 W/L, or from about 20 W/L toabout 40 W/L.

In some embodiments, the homogenized slurry is applied on the currentcollector using a doctor blade coater, a slot-die coater, a transfercoater, or a spray coater.

In certain embodiments, each of the current collectors of the positiveand negative electrodes is independently stainless steel, titanium,nickel, aluminum, copper or electrically-conductive resin. In certainembodiments, the current collector of the positive electrode is analuminum thin film. In some embodiments, the current collector of thenegative electrode is a copper thin film.

In some embodiments, the coated film is dried for a time period fromabout 1 minute to about 30 minutes, or from about 2 minutes to about 10minutes at a temperature from about 45° C. to about 100° C., or fromabout 55° C. to about 75° C.

In certain embodiments, the coated film is dried by a conveyor hot airdrying oven, a conveyor resistance drying oven, a conveyor inductivedrying oven, or a conveyor microwave drying oven.

In some embodiments, the conveyor moves at a speed from about 2meter/minute to about 30 meter/minute, from about 2 meter/minute toabout 25 meter/minute, from about 2 meter/minute to about 20meter/minute, from about 2 meter/minute to about 16 meter/minute, fromabout 3 meter/minute to about 30 meter/minute, from about 3 meter/minuteto about 20 meter/minute, or from about 3 meter/minute to about 16meter/minute.

In certain embodiments, the active battery electrode material is ananode material, wherein the anode material is selected from the groupconsisting of natural graphite particulate, synthetic graphiteparticulate, Sn particulate, Li₄Ti₅O₁₂ particulate, Si particulate, Si—Ccomposite particulate, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of the method disclosed herein.

FIG. 2 depicts a SEM image of the surface morphology of Example 1, anembodiment of the coated cathode electrode disclosed herein.

FIG. 3 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 2.

FIG. 4 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 4.

FIG. 5 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 6.

FIG. 6 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 8.

FIG. 7 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 10.

FIG. 8 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 12.

FIG. 9 depicts cycling performance of an electrochemical cell containinga cathode and an anode prepared by the method described in Example 14.

FIG. 10 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inExample 15.

FIG. 11 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inExample 16.

FIG. 12 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inExample 17.

FIG. 13 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inExample 18.

FIG. 14 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 1.

FIG. 15 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 2.

FIG. 16 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 3.

FIG. 17 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 4.

FIG. 18 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 5.

FIG. 19 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 6.

FIG. 20 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 7.

FIG. 21 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 8.

FIG. 22 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 9.

FIG. 23 depicts cycling performance of an electrochemical cellcontaining a cathode and an anode prepared by the method described inComparative Example 10.

DETAILED DESCRIPTION OF THE INVENTION

Provided herein is a method of preparing a battery electrode, comprisingthe steps of:

1) pre-treating an active battery electrode material in a first aqueoussolution having a pH from about 2.0 to about 7.5 to form a firstsuspension;

2) drying the first suspension to obtain a pre-treated active batteryelectrode material;

3) dispersing the pre-treated active battery electrode material, aconductive agent, and a binder material in a second aqueous solution toform a slurry;

4) homogenizing the slurry by a homogenizer to obtain a homogenizedslurry;

5) applying the homogenized slurry on a current collector to form acoated film on the current collector; and

6) drying the coated film on the current collector to form the batteryelectrode.

The term “electrode” refers to a “cathode” or an “anode.”

The term “positive electrode” is used interchangeably with cathode.Likewise, the term “negative electrode” is used interchangeably withanode.

The term “acid” includes any molecule or ion that can donate a hydrogenion to another substance, and/or contain completely or partiallydisplaceable H⁺ ions. Some non-limiting examples of suitable acidsinclude inorganic acids and organic acids. Some non-limiting examples ofthe inorganic acid include hydrochloric acid, nitric acid, phosphoricacid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid,perchloric acid, hydroiodic acid, and combinations thereof. Somenon-limiting examples of the organic acids include acetic acid, lacticacid, oxalic acid, citric acid, uric acid, trifluoroacetic acid,methanesulfonic acid, formic acid, propionic acid, butyric acid, valericacid, gluconic acid, malic acid, caproic acid, and combinations thereof.

The term “acidic solution” refers to a solution of a soluble acid,having a pH lower than 7.0, lower than 6.5, lower than 6.0, lower than5.0, lower than 4.0, lower than 3.0, or lower than 2.0. In someembodiments, the pH is greater than 6.0, greater than 5.0, greater than4.0, greater than 3.0, or greater than 2.0.

The term “pre-treating” as used herein refers to an act of improving oraltering the properties of a material, or removing any contaminants in amaterial by acting upon with some agents, or an act of suspending amaterial in some solvents.

The term “dispersing” as used herein refers to an act of distributing achemical species or a solid more or less evenly throughout a fluid.

The term “binder material” refers to a chemical or a substance that canbe used to hold the active battery electrode material and conductiveagent in place.

The term “homogenizer” refers to an equipment that can be used forhomogenization of materials. The term “homogenization” refers to aprocess of reducing a substance or material to small particles anddistributing it uniformly throughout a fluid. Any conventionalhomogenizers can be used for the method disclosed herein. Somenon-limiting examples of the homogenizer include stirring mixers,blenders, mills (e.g., colloid mills and sand mills), ultrasonicators,atomizers, rotor-stator homogenizers, and high pressure homogenizers.

The term “ultrasonicator” refers to an equipment that can applyultrasound energy to agitate particles in a sample. Any ultrasonicatorthat can disperse the slurry disclosed herein can be used herein. Somenon-limiting examples of the ultrasonicator include an ultrasonic bath,a probe-type ultrasonicator, and an ultrasonic flow cell.

The term “ultrasonic bath” refers to an apparatus through which theultrasonic energy is transmitted via the container's wall of theultrasonic bath into the liquid sample.

The term “probe-type ultrasonicator” refers to an ultrasonic probeimmersed into a medium for direct sonication. The term “directsonication” means that the ultrasound is directly coupled into theprocessing liquid.

The term “ultrasonic flow cell” or “ultrasonic reactor chamber” refersto an apparatus through which sonication processes can be carried out ina flow-through mode. In some embodiments, the ultrasonic flow cell is ina single-pass, multiple-pass or recirculating configuration.

The term “planetary mixer” refers to an equipment that can be used tomix or blend different materials for producing a homogeneous mixture,which consists of a single or double blade with a high speed dispersionblade. The rotational speed can be expressed in unit of rotations perminute (rpm) which refers to the number of rotations that a rotatingbody completes in one minute.

The term “applying” as used herein in general refers to an act of layingor spreading a substance on a surface.

The term “current collector” refers to a support for coating the activebattery electrode material and a chemically inactive high electronconductor for keeping an electric current flowing to electrodes duringdischarging or charging a secondary battery.

The term “room temperature” refers to indoor temperatures from about 18°C. to about 30° C., e.g., 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, or 30° C. In some embodiments, room temperature refers to atemperature of about 20° C. +/−1° C. or +/−2° C. or +/−3° C. In otherembodiments, room temperature refers to a temperature of about 22° C. orabout 25° C.

The term “C rate” refers to the charging or discharging rate of a cellor battery, expressed in terms of its total storage capacity in Ah ormAh. For example, a rate of 1 C means utilization of all of the storedenergy in one hour; a 0.1 C means utilization of 10% of the energy inone hour and the full energy in 10 hours; and a 5 C means utilization ofthe full energy in 12 minutes.

The term “ampere-hour (Ah)” refers to a unit used in specifying thestorage capacity of a battery. For example, a battery with 1 Ah capacitycan supply a current of one ampere for one hour or 0.5 A for two hours,etc. Therefore, 1 Ampere-hour (Ah) is the equivalent of 3600 coulombs ofelectrical charge. Similarly, the term “miniampere-hour (mAh)” alsorefers to a unit of the storage capacity of a battery and is 1/1,000 ofan ampere-hour.

The term “doctor blading” refers to a process for fabrication of largearea films on rigid or flexible substrates. A coating thickness can becontrolled by an adjustable gap width between a coating blade and acoating surface, which allows the deposition of variable wet layerthicknesses.

The term “transfer coating” or “roll coating” refers to a process forfabrication of large area films on rigid or flexible substrates. Aslurry is applied on the substrate by transferring a coating from thesurface of a coating roller with pressure. A coating thickness can becontrolled by an adjustable gap width between a metering blade and asurface of the coating roller, which allows the deposition of variablewet layer thicknesses. In a metering roll system, the thickness of thecoating is controlled by adjusting the gap between a metering roller anda coating roller.

The term “battery cycle life” refers to the number of completecharge/discharge cycles a battery can perform before its nominalcapacity falls below 80% of its initial rated capacity.

The term “major component” of a composition refers to the component thatis more than 50%, more than 55%, more than 60%, more than 65%, more than70%, more than 75%, more than 80%, more than 85%, more than 90%, or morethan 95% by weight or volume, based on the total weight or volume of thecomposition.

The term “minor component” of a composition refers to the component thatis less than 50%, less than 45%, less than 40%, less than 35%, less than30%, less than 25%, less than 20%, less than 15%, less than 10%, or lessthan 5% by weight or volume, based on the total weight or volume of thecomposition.

The term “relatively slow rate” as used herein refers to the loss ofsolvent from the wet solid in the coated film over a relatively longperiod of time. In some embodiments, the time required for drying thecoated film of a designated coating composition at a relatively slowrate is from about 5 minutes to about 20 minutes.

The term “relatively quick drying rate” as used herein refers to theloss of solvent from the wet solid in the coated film over a relativelyshort period of time. In some embodiments, the time required for dryingthe coated film of a designated coating composition at a relativelyquick drying rate is from about 1 minute to about 5 minutes.

In the following description, all numbers disclosed herein areapproximate values, regardless whether the word “about” or “approximate”is used in connection therewith. They may vary by 1 percent, 2 percent,5 percent, or, sometimes, 10 to 20 percent. Whenever a numerical rangewith a lower limit, R^(L), and an upper limit, R^(U), is disclosed, anynumber falling within the range is specifically disclosed. Inparticular, the following numbers within the range are specificallydisclosed: R=R^(L)+k*(R^(U)−R^(L)), wherein k is a variable ranging from1 percent to 100 percent with a 1 percent increment, i.e., k is 1percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent,51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98percent, 99 percent, or 100 percent. Moreover, any numerical rangedefined by two R numbers as defined in the above is also specificallydisclosed.

FIG. 1 shows an embodiment of the method disclosed herein, in which afirst suspension is prepared by pre-treating an active battery electrodematerial in a first aqueous solution having a pH from about 2.0 to about7.5 to form a first suspension. The first suspension is then dried toobtain a pre-treated active battery electrode material. A slurry isprepared by mixing the pre-treated active battery electrode material, aconductive agent, and a binder material in a second aqueous solution.Further components may be added. The slurry is then homogenized by ahomogenizer to obtain a homogenized slurry. A current collector iscoated with the homogenized slurry, and the coated collector is thendried to form the battery electrode.

In certain embodiments, the first suspension is prepared by pre-treatingan active battery electrode material in a first aqueous solution havinga pH from about 2.0 to about 7.5.

Any temperature that can pre-treat the active battery electrode materialcan be used herein. In some embodiments, the active battery electrodematerial can be added to the stirring first aqueous solution at about14° C., about 16° C., about 18° C., about 20° C., about 22° C., about24° C., or about 26° C. In certain embodiments, the pre-treating processcan be performed with heating at a temperature from about 30° C. toabout 80° C., from about 35° C. to about 80° C., from about 40° C. toabout 80° C., from about 45° C. to about 80° C., from about 50° C. toabout 80° C., from about 55° C. to about 80° C., from about 55° C. toabout 70° C., from about 45° C. to about 85° C., or from about 45° C. toabout 90° C. In some embodiments, the pre-treating process can beperformed at a temperature below 30° C., below 25° C., below 22° C.,below 20° C., below 15° C., or below 10° C.

In some embodiments, the active battery electrode material is a cathodematerial, wherein the cathode material is selected from the groupconsisting of LiCoO₂, LiNiO₂, LiNi_(x)Mn_(y)O₂,Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂, LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅,LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄, LiFeO₂, LiFePO₄, andcombinations thereof, wherein each x is independently from 0.3 to 0.8;each y is independently from 0.1 to 0.45; and each z is independentlyfrom 0 to 0.2. In certain embodiments, the cathode material is selectedfrom the group consisting of LiCoO₂, LiNiO₂, LiNi_(x)Mn_(y)O₂,Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂ (NMC), LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅,LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄, LiFeO₂, LiFePO₄, andcombinations thereof, wherein each x is independently from 0.4 to 0.6;each y is independently from 0.2 to 0.4; and each z is independentlyfrom 0 to 0.1. In other embodiments, the cathode material is not LiCoO₂,LiNiO₂, LiV₂O₅, LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄, LiFeO₂, orLiFePO₄. In further embodiments, the cathode material is notLiNi_(x)Mn_(y)O₂, Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂, orLiNi_(x)Co_(y)Al_(z)O₂, wherein each x is independently from 0.3 to 0.8;each y is independently from 0.1 to 0.45; and each z is independentlyfrom 0 to 0.2.

In certain embodiments, the cathode material is doped with a dopantselected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La,Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In some embodiments,the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si, or Ge. Incertain embodiments, the dopant is not Al, Sn, or Zr.

In some embodiments, the cathode material comprises or is a core-shellcomposite comprising a core comprising a lithium transition metal oxideand a shell formed by coating the surface of the core with a transitionmetal oxide. In certain embodiments, the lithium transition metal oxideis selected from the group consisting of LiCoO₂, LiNiO₂,LiNi_(x)Mn_(y)O₂, Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂,LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅, LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄,LiFeO₂, LiFePO₄, and combinations thereof, wherein each x isindependently from 0.3 to 0.8; each y is independently from 0.1 to 0.45;and each z is independently from 0 to 0.2. In some embodiments, thetransition metal oxide is selected from the group consisting of Fe₂O₃,MnO₂, Al₂O₃, MgO, ZnO, TiO₂, La₂O₃, CeO₂, SnO₂, ZrO₂, RuO₂, andcombinations thereof.

In certain embodiments, the cathode material comprises or is acore-shell composite having a core and shell structure, wherein the coreand the shell each independently comprise a lithium transition metaloxide selected from the group consisting of LiCoO₂, LiNiO₂,LiNi_(x)Mn_(y)O₂, Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂,LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅, LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄,LiFeO₂, LiFePO₄, and combinations thereof, wherein each x isindependently from 0.3 to 0.8; each y is independently from 0.1 to 0.45;and each z is independently from 0 to 0.2. In other embodiments, thecore and the shell each independently comprise two or more lithiumtransition metal oxides. The two or more lithium transition metal oxidesin the core and the shell may be the same, or may be different orpartially different. In some embodiments, the two or more lithiumtransition metal oxides are uniformly distributed over the core. Incertain embodiments, the two or more lithium transition metal oxides arenot uniformly distributed over the core.

In some embodiments, each of the lithium transition metal oxides in thecore and the shell is independently doped with a dopant selected fromthe group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru,Si, Ge, and combinations thereof. In certain embodiments, the core andthe shell each independently comprise two or more doped lithiumtransition metal oxides. In some embodiments, the two or more dopedlithium transition metal oxides are uniformly distributed over the core.In certain embodiments, the two or more doped lithium transition metaloxides are not uniformly distributed over the core.

In some embodiments, the diameter of the core is from about 5 μm toabout 45 μm, from about 5 μm to about 35 μm, from about 5 μm to about 25μm, from about 10 μm to about 40 μm, or from about 10 μm to about 35 μm.In certain embodiments, the thickness of the shell is from about 3 μm toabout 15 μm, from about 15 μm to about 45 μm, from about 15 μm to about30 μm, from about 15 μm to about 25 μm, from about 20 μm to about 30 μm,or from about 20 μm to about 35 μm. In certain embodiments, the diameteror thickness ratio of the core and the shell are in the range of 15:85to 85:15, 25:75 to 75:25, 30:70 to 70:30, or 40:60 to 60:40. In certainembodiments, the volume or weight ratio of the core and the shell is80:20, 70:30, 60:40, 50:50, 40:60, or 30:70.

In certain embodiments, the first aqueous solution is a solutioncontaining water as the major component and a volatile solvent, such asalcohols, lower aliphatic ketones, lower alkyl acetates or the like, asthe minor component in addition to water. In certain embodiments, theamount of water is at least 50%, at least 55%, at least 60%, at least65%, at least 70%, at least 75%, at least 80%, at least 85%, at least90%, or at least 95% to the total amount of water and solvents otherthan water. In some embodiments, the amount of water is at most 55%, atmost 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most85%, at most 90%, or at most 95% to the total amount of water andsolvents other than water. In some embodiments, the first aqueoussolution consists solely of water, that is, the proportion of water inthe first aqueous solution is 100 vol. %.

Any water-miscible solvents can be used as the minor component. Somenon-limiting examples of the minor component (i.e., solvents other thanwater) include alcohols, lower aliphatic ketones, lower alkyl acetatesand combinations thereof. Some non-limiting examples of the alcoholinclude C₂-C₄ alcohols, such as methanol, ethanol, isopropanol,n-propanol, butanol, and combinations thereof. Some non-limitingexamples of the lower aliphatic ketones include acetone, dimethylketone, and methyl ethyl ketone. Some non-limiting examples of the loweralkyl acetates include ethyl acetate, isopropyl acetate, and propylacetate.

In certain embodiments, the volatile solvent or the minor component ismethyl ethyl ketone, ethanol, ethyl acetate or a combination thereof.

In some embodiments, the first aqueous solution is a mixture of waterand one or more water-miscible minor component. In certain embodiments,the first aqueous solution is a mixture of water and a minor componentselected from ethanol, isopropanol, n-propanol, t-butanol, n-butanol,and combinations thereof. In some embodiments, the volume ratio of waterand the minor component is from about 51:49 to about 100:1.

In certain embodiments, the first aqueous solution is water. Somenon-limiting examples of water include tap water, bottled water,purified water, pure water, distilled water, de-ionized water, D₂O, or acombination thereof. In some embodiments, the first aqueous solution isde-ionized water. In certain embodiments, the first aqueous solution isfree of alcohol, aliphatic ketone, alkyl acetate, or a combinationthereof.

In some embodiments, the first aqueous solution is acidic, slightlyalkaline, or neutral, and has a pH anywhere within the range of about2.0 to about 8.0. In certain embodiments, the pH of the first aqueoussolution is from about 2.0 to about 7.5, from about 3.0 to about 7.5,from about 4.0 to about 7.5, from about 4.0 to about 7.0, from about 5.0to about 7.5, from about 6.0 to about 7.5, or from about 6.0 to about7.0. In some embodiments, the pH of the first aqueous solution is about7.0, about 6.5, about 6.0, about 5.5, about 5.0, or about 4.0. In otherembodiments, the pH of the first aqueous solution is from about 2 toabout 7, from about 2 to about 6, from about 2 to about 5, or from about2 to about 4. In some embodiments, the pH of the first aqueous solutionis less than about 7, less than about 6, less than about 5, less thanabout 4, or less than about 3.

In certain embodiments, the first aqueous solution comprises one or moreacids selected from the group consisting of inorganic acids, organicacids, and combinations thereof.

In some embodiments, the acid is a mixture of one or more inorganicacids and one or more organic acids, wherein a weight ratio of the oneor more inorganic acids to the one or more organic acids is from about10/1 to about 1/10, from about 8/1 to about 1/8, from about 6/1 to about1/6, or from about 4/1 to about 1/4.

In certain embodiments, the one or more inorganic acids are selectedfrom the group consisting of hydrochloric acid, nitric acid, phosphoricacid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid,perchloric acid, hydroiodic acid, and combinations thereof. In furtherembodiments, the one or more inorganic acids are sulfuric acid,hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, andcombinations thereof. In still further embodiments, the inorganic acidis hydrochloric acid. In some embodiments, the acid is free of inorganicacid such as hydrochloric acid, nitric acid, phosphoric acid, sulfuricacid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid,or hydroiodic acid.

In some embodiments, the one or more organic acids are selected from thegroup consisting of acetic acid, lactic acid, oxalic acid, citric acid,uric acid, trifluoroacetic acid, methanesulfonic acid, formic acid,propionic acid, butyric acid, valeric acid, gluconic acid, malic acid,caproic acid, and combinations thereof. In further embodiments, the oneor more organic acids are formic acid, acetic acid, propionic acid, andcombinations thereof. In still further embodiments, the organic acid isacetic acid. In some embodiments, the acid is free of organic acid suchas acetic acid, lactic acid, oxalic acid, citric acid, uric acid,trifluoroacetic acid, methanesulfonic acid, formic acid, propionic acid,butyric acid, valeric acid, gluconic acid, malic acid, or caproic acid.

The pH of the first aqueous solution is maintained during the additionof the active battery electrode material at a range from about 4.0 toabout 7.5 by addition of one or more acids as a pH adjuster. The choiceof the pH adjuster is not critical. Any suitable organic or inorganicacid may be used. In some embodiments, the pH adjuster is an acidselected from the group consisting of an inorganic acid, an organicacid, and combinations thereof. The pH can be monitored by a pHmeasuring device such as pH sensors. In some embodiments, more than onepH sensors are used for monitoring the pH value.

When the cathode material having a core-shell structure is exposed to anaqueous acidic solution, the shell of the core-shell composite will bedamaged by the acidic environment, thereby affecting the performance ofthe cathode material. In some embodiments, the shell of the core-shellcomposite is very thin and has a thickness from about 3 μm to about 15μm. The thin layer is very fragile and can therefore easily be damaged.In certain embodiments, the first aqueous solution is slightly alkalineor neutral, and has a pH anywhere within the range from about 7.0 toabout 7.5 or from about 7.0 to about 8.0. In some embodiments, thecore-shell composite is pre-treated in water, alcohol, or a mixture ofwater and alcohol. In one embodiment, the first aqueous solution iswater and contaminants such as dirt and water-soluble impurities can beremoved from the surface of the core-shell composite without damagingthe shell. In another embodiment, the first aqueous solution is analcohol or a mixture of water and alcohol, and contaminants such asdirt, organic compounds such as grease and oil, and water-solubleimpurities can be removed from the surface of the core-shell compositewithout damaging the shell. In further embodiments, the alcohol isselected from the group consisting of methanol, ethanol, propanol,butanol, pentanol, and isomers and combinations thereof.

The use of the aqueous acidic solution for pre-treating the Ni-richcathode material such as NMC532, NMC622, or NMC811 may result in defectson the surface of the cathode material. These defects in turn cause mildto severe degradation of electrochemical performance of anelectrochemical cell. Acid pretreatment may also lead to surfaceirregularities of the cathode material, which in turn cause reduced cellperformance or even cell failure. In some embodiments, the Ni-richcathode material is pre-treated in a slightly alkaline or neutralenvironment. In certain embodiments, the first aqueous solution has a pHanywhere within the range from about 7.0 to about 7.5 or from about 7.0to about 8.0. In some embodiments, the Ni-rich cathode material ispre-treated in water, alcohol or a mixture of water and alcohol. Inother embodiments, the Ni-rich cathode material is pre-treated in aslightly acidic environment having a pH from about 6.0 to about 7.0. Infurther embodiments, the first aqueous solution comprises an acid in anamount from about 0.001 wt. % to about 0.01 wt. %. In other embodiments,the first aqueous solution comprises an acid in an amount of less thanabout 0.01 wt. %. Therefore, contaminants can be removed from thesurface of the Ni-rich cathode material without creating surface defectsfor the cathode material.

In some embodiments, after adding the active battery electrode materialto the first aqueous solution, the mixture can be further stirred for atime period sufficient for forming the first suspension. In certainembodiments, the time period is from about 5 minutes to about 2 hours,from about 5 minutes to about 1.5 hours, from about 5 minutes to about 1hour, from about 5 minutes to about 30 minutes, from about 5 minutes toabout 15 minutes, from about 10 minutes to about 2 hours, from about 10minutes to about 1.5 hours, from about 10 minutes to about 1 hour, fromabout 10 minutes to about 30 minutes, from about 15 minutes to about 1hour, or from about 30 minutes to about 1 hour.

In certain embodiments, the active battery electrode material is ananode material, wherein the anode material is selected from the groupconsisting of natural graphite particulate, synthetic graphiteparticulate, Sn (tin) particulate, Li₄Ti₅O₁₂ particulate, Si (silicon)particulate, Si—C composite particulate, and combinations thereof.

In some embodiments, the first suspension can be dried to obtain apre-treated active battery electrode material. Any dryer that can dry asuspension can be used herein. In some embodiments, the drying processis performed by a double-cone vacuum dryer, a microwave dryer, or amicrowave vacuum dryer.

Conventionally, metal material is not suggested to use microwave dryerto dry as the characteristic of metal material can reflect microwavefrequency. To our surprise, when drying is performed by a microwavedryer or microwave vacuum dryer, the cathode material can be effectivelydried and drying time can be significantly shortened, thereby loweringoperational costs. In some embodiments, the drying time is from about 3minutes to about 25 minutes. Furthermore, drying the cathode material athigh temperatures for long time may result in undesirable decompositionof the cathode material, and alter oxidation states of the cathodematerial. The cathode material having high nickel and/or manganesecontent is particularly temperature sensitive. As such, the positiveelectrode may have reduced performance. Therefore, decreased dryingtimes significantly reduce or eliminate degradation of the cathodematerial. In certain embodiments, the dryer is a microwave dryer or amicrowave vacuum dryer. In some embodiments, the microwave dryer ormicrowave vacuum dryer is operated at a power from about 500 W to about3 kW, from about 5 kW to about 15 kW, from about 6 kW to about 20 kW,from about 7 kW to about 20 kW, from about 15 kW to about 70 kW, fromabout 20 kW to about 90 kW, from about 30 kW to about 100 kW, or fromabout 50 kW to about 100 kW.

In some embodiments, the drying step can be carried out for a timeperiod that is sufficient for drying the first suspension. In certainembodiments, the drying time is from about 3 minutes to about 2 hours,from about 5 minutes to about 2 hours, from about 10 minutes to about 3hours, from about 10 minutes to about 4 hours, from about 15 minutes toabout 4 hours, or from about 20 minutes to about 5 hours.

After formation of the pre-treated active battery electrode material bydrying the first suspension, a slurry can be formed by dispersing thepre-treated active battery electrode material, a conductive agent, and abinder material in a second aqueous solution.

In certain embodiments, the amount of the pre-treated active batteryelectrode material is at least 1%, at least 2%, at least 3%, at least4%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%,at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, atleast 55%, at least 60%, at least 65%, at least 70%, at least 75%, atleast 80%, at least 85%, at least 90%, or at least 95% by weight orvolume, based on the total weight or volume of the slurry. In someembodiments, the amount of the pre-treated active battery electrodematerial is at most 1%, at most 2%, at most 3%, at most 4%, at most 5%,at most 10%, at most 15%, at most 20%, at most 25%, at most 30%, at most35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, atmost 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most90%, or at most 95% by weight or volume, based on the total weight orvolume of the slurry.

In some embodiments, the pre-treated active battery electrode materialis the major component of the slurry. In some embodiments, thepre-treated active battery electrode material is present in an amountfrom about 50% to about 95% by weight or volume, from about 55% to about95% by weight or volume, from about 60% to about 95% by weight orvolume, from about 65% to about 95% by weight or volume, from about 70%to about 95% by weight or volume, from about 75% to about 95% by weightor volume, from about 80% to about 95% by weight or volume, from about85% to about 95% by weight or volume, from about 55% to about 85% byweight or volume, from about 60% to about 85% by weight or volume, fromabout 65% to about 85% by weight or volume, from about 70% to about 85%by weight or volume, from about 65% to about 80% by weight or volume, orfrom about 70% to about 80% by weight or volume, based on the totalweight or volume of the slurry.

The conductive agent in the slurry is for enhancing theelectrically-conducting property of an electrode. In some embodiments,the conductive agent is selected from the group consisting of carbon,carbon black, graphite, expanded graphite, graphene, graphenenanoplatelets, carbon fibres, carbon nano-fibers, graphitized carbonflake, carbon tubes, carbon nanotubes, activated carbon, mesoporouscarbon, and combinations thereof. In certain embodiments, the conductiveagent is not carbon, carbon black, graphite, expanded graphite,graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers,graphitized carbon flake, carbon tubes, carbon nanotubes, activatedcarbon, or mesoporous carbon.

The binder material in the slurry performs a role of binding the activebattery electrode material and conductive agent together on the currentcollector. In some embodiments, the binder material is selected from thegroup consisting of styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrilecopolymer, polyacrylic acid (PAA), polyacrylonitrile, poly(vinylidenefluoride)-hexafluoropropene (PVDF-HFP), latex, a salt of alginic acid,and combinations thereof. In certain embodiments, the salt of alginicacid comprises a cation selected from Na, Li, K, Ca, NH₄, Mg, Al, or acombination thereof.

In some embodiments, the binder material is SBR, CMC, PAA, a salt ofalginic acid, or a combination thereof. In certain embodiments, thebinder material is acrylonitrile copolymer. In some embodiments, thebinder material is polyacrylonitrile. In certain embodiments, the bindermaterial is free of styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), polyvinylidene fluoride (PVDF), acrylonitrilecopolymer, polyacrylic acid (PAA), polyacrylonitrile, poly(vinylidenefluoride)-hexafluoropropene (PVDF-HFP), latex, or a salt of alginicacid.

In certain embodiments, the amount of each of the conductive agent andbinder material is independently at least 1%, at least 2%, at least 3%,at least 4%, at least 5%, at least 10%, at least 15%, at least 20%, atleast 25%, at least 30%, at least 35%, at least 40%, at least 45%, or atleast 50% by weight or volume, based on based on the total weight orvolume of the slurry. In some embodiments, the amount of each of theconductive agent and binder material is independently at most 1%, atmost 2%, at most 3%, at most 4%, at most 5%, at most 10%, at most 15%,at most 20%, at most 25%, at most 30%, at most 35%, at most 40%, at most45%, or at most 50% by weight or volume, based on the total weight orvolume of the slurry.

In some embodiments, the conductive agent is pre-treated in an alkalineor basic solution prior to step 3). Pre-treating the conductive agentbefore the slurry preparation can enhance wettability and dispersingcapability of the conductive agent in the slurry, thus allowinghomogeneous distribution of the conductive agent within the driedcomposite electrode. If particulates of the conductive agent aredispersed heterogeneously in the electrode, the battery performance,life, and safety will be affected.

In certain embodiments, the conductive agent can be pre-treated for atime period from about 30 minutes to about 2 hours, from about 30minutes to about 1.5 hours, from about 30 minutes to about 1 hour, fromabout 45 minutes to about 2 hours, from about 45 minutes to about 1.5hours, or from about 45 minutes to about 1 hour. In some embodiments,the alkaline or basic solution comprises a base selected from the groupconsisting of H₂O₂, LiOH, NaOH, KOH, NH₃.H₂O, Be(OH)₂, Mg(OH)₂, Ca(OH)₂,Li₂CO₃, Na₂CO₃, NaHCO₃, K₂CO₃, KHCO₃, and combinations thereof. Incertain embodiments, the basic solution comprises an organic base. Insome embodiments, the basic solution is free of organic base. In certainembodiments, the basic solution is free of H₂O₂, LiOH, NaOH, KOH,NH₃.H₂O, Be(OH)₂, Mg(OH)₂, Ca(OH)₂, Li₂CO₃, Na₂CO₃, NaHCO₃, K₂CO₃ orKHCO₃. It is desired to keep the particulate dispersed uniformly withina slurry. Pretreating the conductive agent with an alkaline solution canwash away impurity such as oil and grease, promote more uniformdistribution of particles of the conductive agent and improve itsdispensability in the slurry without accumulating the alkaline impuritywhich has negative impact on battery performance. Compared to addingdispersing agent, the dispersing agent will stay in the slurry and maynegatively impact battery performance.

In some embodiments, the pH of the alkaline or basic solution is greaterthan 7, greater than 8, greater than 9, greater than 10, greater than11, greater than 12, or greater than 13. In some embodiments, the pH ofthe alkaline or basic solution is less than 8, less than 9, less than10, less than 11, less than 12, or less than 13.

In certain embodiments, the conductive agent is dispersed in a thirdaqueous solution to form a second suspension prior to step 3).

Compared to an active battery electrode material, a conductive agent hasa relatively high specific surface area. Therefore, the conductive agenthas a tendency to agglomerate due to its relatively high specificsurface area, especially when the particulates of the conductive agentmust be dispersed in a highly dense suspension of the active batteryelectrode material. Dispersing the conductive agent before the slurrypreparation can minimize the particles from agglomerating, thus allowingmore homogeneous distribution of the conductive agent within the driedcomposite electrode. This could reduce internal resistance and enhanceelectrochemical performance of electrode materials.

Each of the pre-treated active battery electrode material, conductiveagent, and binder material can be independently added to the secondaqueous solution in one portion, thereby greatly simplifying the methodof the present invention.

In some embodiments, the amount of the conductive agent in the secondsuspension is from about 0.05 wt. % to about 0.5 wt. %, from about 0.1wt. % to about 1 wt. %, from about 0.25 wt. % to about 2.5 wt. %, fromabout 0.5 wt. % to about 5 wt. %, from about 2 wt. % to about 5 wt. %,from about 3 wt. % to about 7 wt. %, or from about 5 wt. % to about 10wt. %, based on the total weight of the mixture of the conductive agentand the third aqueous solution.

In certain embodiments, the binder material is dissolved in a fourthaqueous solution to form a resulting solution or a binder solution priorto step 3).

Dispersing the solid binder material before the slurry preparation canprevent adhesion of the solid binder material to the surface of othermaterials, thus allowing the binder material to disperse homogeneouslyinto the slurry. If the binder material is dispersed heterogeneously inthe electrode, the performance of the battery may deteriorate.

In some embodiments, the amount of the binder material in the bindersolution is from about 3 wt. % to about 6 wt. %, from about 5 wt. % toabout 10 wt. %, from about 7.5 wt. % to about 15 wt. %, from about 10wt. % to about 20 wt. %, from about 15 wt. % to about 25 wt. %, fromabout 20 wt. % to about 40 wt. %, or from about 35 wt. % to about 50 wt.%, based on the total weight of the mixture of the binder material andthe fourth aqueous solution.

In certain embodiments, each of the second, third and fourth aqueoussolutions independently is a solution containing water as the majorcomponent and a volatile solvent, such as alcohols, lower aliphaticketones, lower alkyl acetates or the like, as the minor component inaddition to water. In certain embodiments, the amount of water in eachsolution is independently at least 55%, at least 60%, at least 65%, atleast 70%, at least 75%, at least 80%, at least 85%, at least 90%, or atleast 95% to the total amount of water and solvents other than water. Insome embodiments, the amount of water is at most 55%, at most 60%, atmost 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most90%, or at most 95% to the total amount of water and solvents other thanwater. In some embodiments, each of the second, third and fourth aqueoussolutions independently consists solely of water, that is, theproportion of water in each solution is 100 vol. %.

Any water-miscible solvents can be used as the minor component of thesecond, third or fourth aqueous solution. Some non-limiting examples ofthe minor component include alcohols, lower aliphatic ketones, loweralkyl acetates and combinations thereof. Some non-limiting examples ofthe alcohol include C₂-C₄ alcohols, such as methanol, ethanol,isopropanol, n-propanol, butanol, and combinations thereof. Somenon-limiting examples of the lower aliphatic ketones include acetone,dimethyl ketone, and methyl ethyl ketone. Some non-limiting examples ofthe lower alkyl acetates include ethyl acetate, isopropyl acetate, andpropyl acetate.

In some embodiments, the volatile solvent or minor component is methylethyl ketone, ethanol, ethyl acetate or a combination thereof.

In some embodiments, the composition of the slurry does not requireorganic solvents. In certain embodiments, each of the second, third andfourth aqueous solutions independently is water. Some non-limitingexamples of water include tap water, bottled water, purified water, purewater, distilled water, de-ionized water, D₂O, or a combination thereof.In some embodiments, each of the second, third and fourth aqueoussolutions independently is purified water, pure water, de-ionized water,distilled water, or a combination thereof. In certain embodiments, eachof the second, third and fourth aqueous solutions is free of an organicsolvent such as alcohols, lower aliphatic ketones, lower alkyl acetates.Since the composition of the slurry does not contain any organicsolvent, expensive, restrictive and complicated handling of organicsolvents is avoided during the manufacture of the slurry.

Any temperature that can be used in the dispersing step to form theslurry can be used herein. In some embodiments, the pre-treated activebattery electrode material, conductive agent and binder material areadded to the stirring second aqueous solution at about 14° C., about 16°C., about 18° C., about 20° C., about 22° C., about 24° C., or about 26°C. In certain embodiments, the dispersing process can be performed withheating at a temperature from about 30° C. to about 80° C., from about35° C. to about 80° C., from about 40° C. to about 80° C., from about45° C. to about 80° C., from about 50° C. to about 80° C., from about55° C. to about 80° C., from about 55° C. to about 70° C., from about45° C. to about 85° C., or from about 45° C. to about 90° C. In someembodiments, the dispersing process can be performed at a temperaturebelow 30° C., below 25° C., below 22° C., below 20° C., below 15° C., orbelow 10° C.

Optional components may be used to assist in dispersing the pre-treatedactive battery electrode material, conductive agent and binder materialin the slurry. In some embodiments, the optional component is adispersing agent. Any dispersing agent that can enhance the dispersionmay be added to the slurry disclosed herein. In certain embodiments, thedispersing agent is selected from the group consisting of ethanol,isopropanol, n-propanol, t-butanol, n-butanol, lithium dodecyl sulfate,trimethylhexadecyl ammonium chloride, polyethylene ethoxylate, sodiumdodecylbenzene sulfonate, sodium stearate, and combinations thereof.

In some embodiments, the total amount of the dispersing agent is fromabout 0.1% to about 10%, from about 0.1% to about 8%, from about 0.1% toabout 6%, from about 0.1% to about 5%, from about 0.1% to about 4%, fromabout 0.1% to about 3%, from about 0.1% to about 2%, or from about 0.1%to about 1% by weight, based on the total weight of the slurry.

In some embodiments, each of the second, third and fourth aqueoussolutions independently comprises a dispersing agent for promoting theseparation of particles and/or preventing agglomeration of theparticles. Any surfactant that can lower the surface tension between aliquid and a solid can be used as the dispersing agent.

In certain embodiments, the dispersing agent is a nonionic surfactant,an anionic surfactant, a cationic surfactant, an amphoteric surfactant,or a combination thereof.

Some non-limiting examples of suitable nonionic surfactant include analkoxylated alcohol, a carboxylic ester, a polyethylene glycol ester,and combinations thereof. Some non-limiting examples of suitablealkoxylated alcohol include ethoxylated and propoxylated alcohols. Insome embodiments, the slurry disclosed herein is free of nonionicsurfactant.

Some non-limiting examples of suitable anionic surfactant include a saltof an alkyl sulfate, an alkyl polyethoxylate ether sulfate, an alkylbenzene sulfonate, an alkyl ether sulfate, a sulfonate, asulfosuccinate, a sarcosinate, and combinations thereof. In someembodiments, the anionic surfactant comprises a cation selected from thegroup consisting of sodium, potassium, ammonium, and combinationsthereof. In some embodiments, the slurry disclosed herein is free ofanionic surfactant.

Some non-limiting examples of suitable cationic surfactant include anammonium salt, a phosphonium salt, an imidazolium salt, a sulfoniumsalt, and combinations thereof. Some non-limiting examples of suitableammonium salt include stearyl trimethylammonium bromide (STAB), cetyltrimethylammonium bromide (CTAB), and myristyl trimethylammonium bromide(MTAB), and combinations thereof. In some embodiments, the slurrydisclosed herein is free of cationic surfactant.

Some non-limiting examples of suitable amphoteric surfactant aresurfactants that contain both cationic and anionic groups. The cationicgroup is ammonium, phosphonium, imidazolium, sulfonium, or a combinationthereof. The anionic hydrophilic group is carboxylate, sulfonate,sulfate, phosphonate, or a combination thereof. In some embodiments, theslurry disclosed herein is free of amphoteric surfactant.

The slurry can be homogenized by a homogenizer. Any equipment that canhomogenize the slurry can be used. In some embodiments, the homogenizeris a stirring mixer, a blender, a mill, an ultrasonicator, arotor-stator homogenizer, an atomizer, or a high pressure homogenizer.

In some embodiments, the homogenizer is an ultrasonicator. Anyultrasonicator that can apply ultrasound energy to agitate and disperseparticles in a sample can be used herein. In some embodiments, theultrasonicator is a probe-type ultrasonicator or an ultrasonic flowcell.

In certain embodiments, the slurry is homogenized by mechanical stirringfor a time period from about 2 hours to about 8 hours. In someembodiments, the stirring mixer is a planetary mixer consisting ofplanetary and high speed dispersion blades. In certain embodiments, therotational speed of the planetary blade is from about 20 rpm to about200 rpm and rotational speed of the dispersion blade is from about 1,000rpm to about 3,500 rpm. In further embodiments, the rotational speed ofthe planetary blade is from about 20 rpm to about 150 rpm or from about30 rpm to about 100 rpm, and rotational speed of the dispersion blade isfrom about 1,000 rpm to about 3,000 rpm or from about 1,500 rpm to about2,500 rpm. When the homogenizer is a stirring mixer, the slurry isstirred for at least two hours to ensure sufficient dispersion. If thedispersion is not sufficient, the battery performance such as cycle lifemay be seriously affected. In further embodiments, the stirring time isfrom about 2 hours to about 6 hours, from about 3 hours to about 8hours, from about 3 hours to about 6 hours, or from about 4 hours toabout 8 hours.

In certain embodiments, the ultrasonic flow cell can be operated in aone-pass, multiple-pass or recirculating mode. In some embodiments, theultrasonic flow cell can include a water-cooling jacket to help maintainthe required temperature. Alternatively, a separate heat exchanger maybe used. In certain embodiments, the flow cell can be made fromstainless steel or glass.

In some embodiments, the slurry is homogenized for a time period fromabout 1 hour to about 10 hours, from about 2 hours to about 4 hours,from about 15 minutes to about 4 hours, from about 30 minutes to about 4hours, from about 1 hour to about 4 hours, from about 2 hours to about 5hours, from about 3 hours to about 5 hours, or from about 2 hours toabout 6 hours.

In certain embodiments, the ultrasonicator is operated at a powerdensity from about 10 W/L to about 100 W/L, from about 20 W/L to about100 W/L, from about 30 W/L to about 100 W/L, from about 40 W/L to about80 W/L, from about 40 W/L to about 70 W/L, from about 40 W/L to about 50W/L, from about 40 W/L to about 60 W/L, from about 50 W/L to about 60W/L, from about 20 W/L to about 80 W/L, from about 20 W/L to about 60W/L, or from about 20 W/L to about 40 W/L.

The continuous flow through system has several advantages over thebatch-type processing. By sonication via ultrasonic flow cell, theprocessing capacity becomes significantly higher. The retention time ofthe material in the flow cell can be adjusted by adjusting the flowrate.

By sonication via recirculating mode, the material is recirculated manytimes through the flow cell in a recirculating configuration.Recirculation increases the cumulative exposure time because liquidpasses through the ultrasonic flow cell only once in a single-passconfiguration.

The multiple-pass mode has a multiple flow cell configuration. Thisarrangement allows for a single-pass processing without the need forrecirculation or multiple passes through the system. This arrangementprovides an additional productivity scale-up factor equal to the numberof utilized flow cells.

The homogenizing step disclosed herein reduces or eliminates thepotential aggregation of the active battery electrode material and theconductive agent and enhances dispersion of each ingredient in theslurry.

When the slurry is homogenized by a mill, a media such as balls,pebbles, small rock, sand or other media is used in a stirred mixturealong with the sample material to be mixed. The particles in the mixtureare mixed and reduced in size by impact with rapidly moving surfaces ina mill. In some embodiments, the ball is made of hard materials such assteel, stainless steel, ceramic or zirconium dioxide (ZrO₂). However, itis observed that the mechanical stress during the milling process causesdamages to the structure of the cathode material resulting in distortionor major structural damage such as cracks. The cathode material may alsobe abraded by the ball causing structural damage and irregularly-shapedsurface. These defects in turn cause mild to severe degradation ofelectrochemical performance of an electrochemical cell. The cathodematerial having a core-shell structure is even more susceptible tomechanical damages due to vulnerability of the shell.

The homogenized slurry can be applied on a current collector to form acoated film on the current collector. The current collector acts tocollect electrons generated by electrochemical reactions of the activebattery electrode material or to supply electrons required for theelectrochemical reactions. In some embodiments, each of the currentcollectors of the positive and negative electrodes, which can be in theform of a foil, sheet or film, is independently stainless steel,titanium, nickel, aluminum, copper or electrically-conductive resin. Incertain embodiments, the current collector of the positive electrode isan aluminum thin film. In some embodiments, the current collector of thenegative electrode is a copper thin film.

In some embodiments, the current collector has a thickness from about 6μm to about 100 μm since thickness will affect the volume occupied bythe current collector within a battery and the amount of the activebattery electrode material and hence the capacity in the battery.

In certain embodiments, the coating process is performed using a doctorblade coater, a slot-die coater, a transfer coater, a spray coater, aroll coater, a gravure coater, a dip coater, or a curtain coater. Insome embodiments, the thickness of the coated film on the currentcollector is from about 10 μto about 300 μm, or from about 20 μm toabout 100 μm.

After applying the homogenized slurry on a current collector, the coatedfilm on the current collector can be dried by a dryer to obtain thebattery electrode. Any dryer that can dry the coated film on the currentcollector can be used herein. Some non-limiting examples of the dryerare a batch drying oven, a conveyor drying oven, and a microwave dryingoven. Some non-limiting examples of the conveyor drying oven include aconveyor hot air drying oven, a conveyor resistance drying oven, aconveyor inductive drying oven, and a conveyor microwave drying oven.

In some embodiments, the conveyor drying oven for drying the coated filmon the current collector includes one or more heating sections, whereineach of the heating sections is individually temperature controlled, andwherein each of the heating sections may include independentlycontrolled heating zones.

In certain embodiments, the conveyor drying oven comprises a firstheating section positioned on one side of the conveyor and a secondheating section positioned on an opposing side of the conveyor from thefirst heating section, wherein each of the first and second heatingsections independently comprises one or more heating elements and atemperature control system connected to the heating elements of thefirst heating section and the second heating section in a manner tomonitor and selectively control the temperature of each heating section.

In some embodiments, the conveyor drying oven comprises a plurality ofheating sections, wherein each heating section includes independentheating elements that are operated to maintain a constant temperaturewithin the heating section.

In certain embodiments, each of the first and second heating sectionsindependently has an inlet heating zone and an outlet heating zone,wherein each of the inlet and outlet heating zones independentlycomprises one or more heating elements and a temperature control systemconnected to the heating elements of the inlet heating zone and theoutlet heating zone in a manner to monitor and selectively control thetemperature of each heating zone separately from the temperature controlof the other heating zones.

In some embodiments, the coated film on the current collector can bedried at a temperature from about 50° C. to about 80° C. The temperaturerange means a controllable temperature gradient in which the temperaturegradually rises from the inlet temperature of 50° C. to the outlettemperature of 80° C. The controllable temperature gradient avoids thecoated film on the current collector from drying too rapidly. Drying thecoated film too quickly can degrade materials in the slurry. Drying thecoated film too quickly can also cause stress defects in the electrodebecause the solvent can be removed from the coated film more quicklythan the film can relax or adjust to the resulting volume changes, whichcan cause defects such as cracks. It is believed that avoiding suchdefects can generally enhance performance of the electrode. Furthermore,drying the coated film too quickly can cause the binder material tomigrate and form a layer of the binder material on the surface of theelectrode.

In certain embodiments, the coated film on the current collector isdried at a relatively slow rate. In certain embodiments, the coated filmon the current collector is dried relatively slowly at a constant rate,followed by a relatively quick drying rate.

In some embodiments, the coated film on the current collector can bedried at a temperature from about 45° C. to about 100° C., from about50° C. to about 100° C., from about 55° C. to about 100° C., from about50° C. to about 90° C., from about 55° C. to about 80° C., from about55° C. to about 75° C., from about 55° C. to about 70° C., from about50° C. to about 80° C., or from about 50° C. to about 70° C. In oneembodiment, the coated film on the current collector may be dried at atemperature from about 40° C. to about 55° C. for a time period fromabout 5 minutes to about 10 minutes. The lower drying temperatures mayavoid the undesirable decomposition of cathode material having highnickel and/or manganese content.

In certain embodiments, the conveyor moves at a speed from about 2meter/minute to about 30 meter/minute, from about 2 meter/minute toabout 25 meter/minute, from about 2 meter/minute to about 20meter/minute, from about 2 meter/minute to about 16 meter/minute, fromabout 3 meter/minute to about 30 meter/minute, from about 3 meter/minuteto about 20 meter/minute, or from about 3 meter/minute to about 16meter/minute.

Controlling the conveyor length and speed can regulate the drying timeof the coated film. Therefore, the drying time can be increased withoutincreasing the length of the conveyor. In some embodiments, the coatedfilm on the current collector can be dried for a time period from about1 minute to about 30 minutes, from about 1 minute to about 25 minutes,from about 1 minute to about 20 minutes, from about 1 minute to about 15minutes, from about 1 minute to about 10 minutes, from about 2 minutesto about 15 minutes, or from about 2 minutes to about 10 minutes.

After the coated film on the current collector is dried, the batteryelectrode is formed. In some embodiments, the battery electrode iscompressed mechanically in order to enhance the density of theelectrode.

The method disclosed herein has the advantage that an aqueous solvent isused in the manufacturing process, which can save process time andfacilities by avoiding the need to handle or recycle hazardous organicsolvents. In addition, costs are reduced by simplifying the totalprocess. Therefore, this method is especially suited for industrialprocesses because of its low cost and ease of handling.

In some embodiments, batteries comprising the electrodes prepared by themethod disclosed herein show a capacity retention of at least about 89%,about 94%, about 95%, about 97%, or about 98% after 500 cycles whendischarged at a rate of 1 C. In certain embodiments, batteries show acapacity retention of at least about 83%, about 88%, about 90%, about92%, about 94% about 95% or about 96% after 1,000 cycles when dischargedat a rate of 1 C. In some embodiments, batteries show a capacityretention of at least about 73%, about 77%, about 80%, about 81%, about88%, about 90%, or about 92% after 2,000 cycles when discharged at arate of 1 C.

The following examples are presented to exemplify embodiments of theinvention but are not intended to limit the invention to the specificembodiments set forth. Unless indicated to the contrary, all parts andpercentages are by weight. All numerical values are approximate. Whennumerical ranges are given, it should be understood that embodimentsoutside the stated ranges may still fall within the scope of theinvention. Specific details described in each example should not beconstrued as necessary features of the invention.

EXAMPLES Example 1 A) Pre-treatment of Active Battery Electrode Material

A particulate cathode material LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂ (NMC333)(obtained from Xiamen Tungsten CO. Ltd., China) was added to a stirringsolution containing 50% deionized water and 50% ethanol at roomtemperature to form a suspension having a solid content of about 35% byweight. The pH of the suspension was measured using a pH meter and thepH was about 7. The suspension was further stirred at room temperaturefor 5 hours. Then the suspension was separated and dried by a 2.45 GHzmicrowave dryer (ZY-4HO, obtained from Zhiya Industrial MicrowaveEquipment Co., Ltd., Guangdong, China) at 750 W for 5 minutes to obtaina pre-treated active battery electrode material.

B) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 91 wt. % pre-treatedactive battery electrode material, 4 wt. % carbon black (SuperP; TimcalLtd, Bodio, Switzerland), 4 wt. % polyacrylonitrile (PAN) (LA 132,Chengdu Indigo Power Sources Co., Ltd., China) and 1% isopropanol(obtained from Aladdin Industries Corporation, China) in deionized waterto form a slurry having a solid content of 70 wt. %. The slurry washomogenized by a planetary stirring mixer (200 L mixer, ChienemeiIndustry Co. Ltd., China) for 6 hours operated at a stirring speed of 20rpm and a dispersing speed of 1500 rpm to obtain a homogenized slurry.The formulation of Example 1 is shown in Table 1 below.

C) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 20 μm using a transfer coater (ZY-TSF6-6518,obtained from Jin Fan Zhanyu New Energy Technology Co. Ltd., China) withan area density of about 26 mg/cm². The coated films on the aluminumfoil were dried for 3 minutes by a 24-meter-long conveyor hot air dryingoven as a sub-module of the transfer coater operated at a conveyor speedof about 8 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of55° C. to the outlet temperature of 80° C.

D) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were dried at about 50° C. for 2.4 minute by a24-meter-long conveyor hot air dryer operated at a conveyor speed ofabout 10 meter/minute to obtain a negative electrode.

Morphological Measurement of Example 1

FIG. 2 shows the SEM image of the surface morphology of the coatedcathode electrode after drying. The morphology of the coated cathodeelectrode was characterized by a scanning electron microscope(JEOL-6300, obtained from JEOL, Ltd., Japan). The SEM image clearlyshows a uniform, crack-free and stable coating throughout the electrodesurface. Furthermore, the electrode shows a homogeneous distribution ofthe pre-treated active battery electrode material and conductive agentwithout large agglomerates.

Example 2 Assembling of Pouch-Type Battery

After drying, the resulting cathode film and anode film of Example 1were used to prepare the cathode and anode respectively by cutting intoindividual electrode plates. A pouch cell was assembled by stacking thecathode and anode electrode plates alternatively and then packaged in acase made of an aluminum-plastic laminated film. The cathode and anodeelectrode plates were kept apart by separators and the case waspre-formed. An electrolyte was then filled into the case holding thepacked electrodes in high-purity argon atmosphere with moisture andoxygen content<1 ppm. The electrolyte was a solution of LiPF₆ (1 M) in amixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) anddimethyl carbonate (DMC) in a volume ratio of 1:1:1. After electrolytefilling, the pouch cells were vacuum sealed and then mechanicallypressed using a punch tooling with standard square shape.

Electrochemical Measurements of Example 2 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester (BTS-5V20A, obtained from Neware Electronics Co.Ltd, China) between 3.0 V and 4.3 V. The nominal capacity was about 10Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.3 V.Test result of cyclability performance is shown in FIG. 3. The capacityretention after 450 cycles was about 95.6% of the initial value. Thetest result is shown in Table 2 below.

Example 3 A) Pre-Treatment of Active Battery Electrode Material

A particulate cathode material LiMn₂O₄ (LMO) (obtained from HuaGuanHengYuan LiTech Co. Ltd., Qingdao, China) was added to a stirring 7 wt.% solution of acetic acid in water (obtained from Aladdin IndustriesCorporation, China) at room temperature to form a suspension having asolid content of about 50% by weight. The pH of the suspension wasmeasured using a pH meter and the pH was about 6. The suspension wasfurther stirred at room temperature for 2.5 hours. Then the suspensionwas separated and dried by a 2.45 GHz microwave dryer at 750 W for 5minutes to obtain a pre-treated active battery electrode material.

B) Preparation of Positive Electrode Slurry

Carbon nanotube (NTP2003; Shenzhen Nanotech Port Co., Ltd., China) (25g) was pretreated in 2 L of an alkaline solution containing 0.5 wt. %NaOH for about 15 minutes and then washed by deionized water (5 L). Thetreated carbon nanotube was then dispersed in deionized water to form asuspension having a solid content of 6.25 wt. %.

A positive electrode slurry was prepared by mixing 92 wt. % pre-treatedactive battery electrode material, 3 wt. % carbon black, 1 wt. %suspension of the treated carbon nanotube and 4 wt. % polyacrylonitrilein deionized water to form a slurry having a solid content of 65 wt. %.The slurry was homogenized by a circulating ultrasonic flow cell(NP8000, obtained from Guangzhou Newpower Ultrasonic ElectronicEquipment Co., Ltd., China) for 8 hours operated at 1000 W to obtain ahomogenized slurry. The formulation of Example 3 is shown in Table 1below.

C) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 20 μm using a transfer coater with an area densityof about 40 mg/cm². The coated films on the aluminum foil were dried for6 minutes by a 24-meter-long conveyor hot air drying oven as asub-module of the transfer coater operated at a conveyor speed of about4 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of65° C. to the outlet temperature of 90° C.

D) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were dried at about 50° C. for 2.4 minutes by a24-meter-long conveyor hot air dryer operated at a conveyor speed ofabout 10 meter/minute to obtain a negative electrode.

Example 4 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 4 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.3 V. The nominal capacity wasabout 10 Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.3 V.Test result of cyclability performance is shown in FIG. 4. The capacityretention after 2000 cycles was about 77% of the initial value. The testresult is shown in Table 2 below.

Example 5 A) Pre-Treatment of Active Battery Electrode Material

A particulate cathode material LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂ (NMC333)(obtained from Shenzhen Tianjiao Technology Co. Ltd., China) was addedto a stirring deionized water at room temperature to form a suspensionhaving a solid content of about 65% by weight. The pH of the suspensionwas measured using a pH meter and the pH was about 7. The suspension wasfurther stirred at room temperature for 10 hours. Then the suspensionwas separated and dried by a 2.45 GHz microwave dryer at 750 W for 5minutes to obtain a pre-treated active battery electrode material.

B) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 93 wt. % pre-treatedactive battery electrode material, 3 wt. % carbon black, 0.5 wt. %nonylphenol ethoxylate (TERGITOL™ NP-6, DOW Chemical, US) and 3.5 wt. %polyacrylonitrile in deionized water to form a slurry having a solidcontent of 75 wt. %. The slurry was homogenized by a circulatingultrasonic flow cell for 8 hours operated at 1000 W to obtain ahomogenized slurry. The formulation of Example 5 is shown in Table 1below.

C) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 20 μm using a transfer coater with an area densityof about 32 mg/cm². The coated films on the aluminum foil were dried for4 minutes by a 24-meter-long conveyor hot air drying oven as asub-module of the transfer coater operated at a conveyor speed of about6 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of50° C. to the outlet temperature of 75° C.

D) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon,5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were dried at about 50° C. for 2.4 minutes by a24-meter-long conveyor hot air dryer operated at a conveyor speed ofabout 10 meter/minute to obtain a negative electrode.

Example 6 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 6 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.3 V. The nominal capacity wasabout 10 Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.3 V.Test result of cyclability performance is shown in FIG. 5. The capacityretention after 560 cycles was about 94.8% of the initial value. Thetest result is shown in Table 2 below.

Example 7 A) Pre-Treatment of Active Battery Electrode Material

A particulate cathode material LiFePO₄ (obtained from Xiamen TungstenCo. Ltd., China) was added to a stirring 3 wt. % solution of acetic acidin water (obtained from Aladdin Industries Corporation, China) at roomtemperature to form a suspension having a solid content of about 50% byweight. The pH of the suspension was measured using a pH meter and thepH was about 3.8. The suspension was further stirred at room temperaturefor 2.5 hours. Then the suspension was separated and dried by a 2.45 GHzmicrowave dryer at 700 W for 5 minutes to obtain a pre-treated activebattery electrode material.

B) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 88 wt. % pre-treatedactive battery electrode material, 5.5 wt. % carbon black, 0.5 wt. %nonylphenol ethoxylate (TERGITOL™ NP-6, DOW Chemical, US) and 6 wt. %polyacrylonitrile in deionized water to form a slurry having a solidcontent of 70 wt. %. The slurry was homogenized by a circulatingultrasonic flow cell for 6 hours operated at 1000 W to obtain ahomogenized slurry. The formulation of Example 7 is shown in Table 1below.

C) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 30 μm using a transfer coater with an area densityof about 56 mg/cm². The coated films on the aluminum foil were thendried for 6 minutes by a 24-meter-long conveyor hot air drying oven as asub-module of the transfer coater operated at a conveyor speed of about4 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of75° C. to the outlet temperature of 90° C.

D) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were then dried at about 50° C. for 2.4 minutesby a 24-meter-long conveyor hot air dryer operated at a conveyor speedof about 10 meter/minute to obtain a negative electrode.

Example 8 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 8 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 2.5 V and 3.6 V. The nominal capacity wasabout 3.6 Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 2.5 V and 3.6 V.Test result of cyclability performance is shown in FIG. 6. The capacityretention after 3000 cycles was about 82.6% of the initial value. Thetest result is shown in Table 2 below.

Example 9

A) Preparation of an Active Cathode Material with Core-Shell Structure

The core of the core-shell cathode material wasLi_(1.03)Ni_(0.51)Mn_(0.32)Co_(0.17)O₂ and was prepared by aco-precipitation method. The shell of the core-shell cathode materialwas Li_(0.95)Ni_(0.53)Mn_(0.29)Co_(0.15)Al_(0.03)O₂ and was prepared byforming a precipitate of Al(OH)₃ on the surface of the core to form aprecursor, mixing the precursor with Li₂CO₃ (obtained from TianqiLithium, Shenzhen, China) to obtain a mixture, and calcinating themixture at 900° C. The calcinated product was crushed by a jet mill(LNJ-6A, obtained from Mianyang Liuneng Powder Equipment Co., Ltd.,Sichuan, China) for about 1 hour, followed by passing the crushedproduct through a 270-mesh sieve to obtain a cathode material having aparticle size D50 of about 38 μm. The content of aluminium in thecore-shell cathode material gradiently decreased from the outer surfaceof the shell to the inner core. The thickness of the shell was about 3μm.

B) Pre-Treatment of the Active Battery Electrode Material

The core-shell cathode material (C-S NMC532) prepared above was added toa stirring solution containing 50% deionized water and 50% methanol atroom temperature to form a suspension having a solid content of about50% by weight. The pH of the suspension was measured using a pH meterand the pH was about 7.5. The suspension was further stirred at roomtemperature for 3.5 hours. Then the suspension was separated and driedby a 2.45 GHz microwave dryer at 750 W for 5 minutes to obtain apre-treated active battery electrode material.

C) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 90 wt. % pre-treatedactive battery electrode material, 5 wt. % carbon black (SuperP;obtained from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and5 wt. % polyacrylonitrile (LA 132, Chengdu Indigo Power Sources Co.,Ltd., China) as a binder, which were dispersed in deionized water toform a slurry with a solid content of 50 wt. %. The slurry washomogenized by a planetary stirring mixer for 6 hours operated at astirring speed of 20 rpm and a dispersing speed of 1500 rpm to obtain ahomogenized slurry. The formulation of Example 9 is shown in Table 1below.

D) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 30 μm using a transfer coater with an area densityof about 44 mg/cm². The coated films on the aluminum foil were thendried for 5 minutes by a 24-meter-long conveyor hot air drying oven as asub-module of the transfer coater operated at a conveyor speed of about4 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of67° C. to the outlet temperature of 78° C.

E) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were then dried at about 50° C. for 2.4 minutesby a 24-meter-long conveyor hot air dryer operated at a conveyor speedof about 10 meter/minute to obtain a negative electrode.

Example 10 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 10 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.46 Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in FIG. 7. The capacityretention after 361 cycles was about 98.6% of the initial value. Thetest result is shown in Table 2 below.

Example 11

A) Preparation of an Active Cathode Material with Core-Shell Structure

The core of the core-shell cathode material wasLi_(1.01)Ni_(0.96)Mg_(0.04)O₂ (C—S LNMgO) and was prepared by solidstate reaction in which MgO and NiO_(x) (x=1 to 2) were mixed with LiOHfollowed by calcination at 850° C. The shell of the core-shell cathodematerial was Li_(0.95)Co_(1.1)O₂ and was prepared by forming aprecipitate of Co(OH)₂ on the surface of the core to form a precursor,mixing the precursor with Li₂CO₃ (obtained from Tianqi Lithium,Shenzhen, China) to obtain a mixture, and calcinating the mixture at800° C. The calcinated product was crushed by a jet mill (LNJ-6A,obtained from Mianyang Liuneng Powder Equipment Co., Ltd., Sichuan,China) for about 1 hour, followed by passing the crushed product througha 270-mesh sieve to obtain a cathode material having a particle size D50of about 33 μm. The content of cobalt in the core-shell cathode materialgradiently decreased from the outer surface of the shell to the innercore. The thickness of the shell was about 5 μm.

B) Pre-Treatment of the Active Battery Electrode Material

The core-shell cathode material prepared above was added to a stirringsolution containing 70% deionized water and 30% iso-propanol at roomtemperature to form a suspension having a solid content of about 60% byweight. The pH of the suspension was measured using a pH meter and thepH was about 8.0. The suspension was further stirred at room temperaturefor 6.5 hours. Then the suspension was separated and dried by a 2.45 GHzmicrowave dryer at 750 W for 5 minutes to obtain a pre-treated activebattery electrode material.

C) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 89 wt. % pre-treatedactive battery electrode material, 5.5 wt. % carbon black (SuperP;obtained from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and5.5 wt. % polyacrylonitrile (LA 132, Chengdu Indigo Power Sources Co.,Ltd., China) as a binder, which were dispersed in deionized water toform a slurry with a solid content of 50 wt. %. The slurry washomogenized by a planetary stirring mixer for 6 hours operated at astirring speed of 20 rpm and a dispersing speed of 1500 rpm to obtain ahomogenized slurry. The formulation of Example 11 is shown in Table 1below.

D) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 30 μm using a transfer coater with an area densityof about 42 mg/cm². The coated films on the aluminum foil were thendried for 5.5 minutes by a 24-meter-long conveyor hot air drying oven asa sub-module of the transfer coater operated at a conveyor speed ofabout 4.2 meter/minute to obtain a positive electrode. Thetemperature-programmed oven allowed a controllable temperature gradientin which the temperature gradually rose from the inlet temperature of62° C. to the outlet temperature of 75° C.

E) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were then dried at about 50° C. for 2.4 minutesby a 24-meter-long conveyor hot air dryer operated at a conveyor speedof about 10 meter/minute to obtain a negative electrode.

Example 12 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 12 I) Nominal Capacity

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.4 Ah.

II) Cyclability Performance

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in FIG. 8. The capacityretention after 385 cycles was about 98.1% of the initial value. Thetest result is shown in Table 2 below.

Example 13 A) Pre-Treatment of Active Battery Electrode Material

A particulate cathode material LiCoO₂ (obtained from Xiamen Tungsten CO.Ltd., China) was added to a stirring solution containing 50% deionizedwater and 50% ethanol at room temperature to form a suspension having asolid content of about 2% by weight. The pH of the suspension wasmeasured using a pH meter and the pH was about 7.0. The suspension wasfurther stirred at room temperature for 1 hour. Then the suspension wasseparated and dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained fromZhiya Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750W for 5 minutes to obtain a pre-treated active battery electrodematerial.

B) Preparation of Positive Electrode Slurry

A positive electrode slurry was prepared by mixing 90 wt. % pre-treatedactive battery electrode material, 5 wt. % carbon black (SuperP;obtained from Timcal Ltd, Bodio, Switzerland) as a conductive agent, and5 wt. % polyacrylonitrile (LA 132, Chengdu Indigo Power Sources Co.,Ltd., China) as a binder, which were dispersed in deionized water toform a slurry with a solid content of 50 wt. %. The slurry washomogenized by a planetary stirring mixer for 6 hours operated at arotation speed of 30 rpm and a dispersing speed of 1500 rpm to obtain ahomogenized slurry. The formulation of Example 13 is shown in Table 1below.

C) Preparation of Positive Electrode

The homogenized slurry was coated onto both sides of an aluminum foilhaving a thickness of 20 μm using a transfer coater (ZY-TSF6-6518,obtained from Jin Fan Zhanyu New Energy Technology Co. Ltd., China) withan area density of about 26 mg/cm². The coated films on the aluminumfoil were dried for 3.4 minutes by a 24-meter-long conveyor hot airdrying oven as a sub-module of the transfer coater operated at aconveyor speed of about 7 meter/minute to obtain a positive electrode.The temperature-programmed oven allowed a controllable temperaturegradient in which the temperature gradually rose from the inlettemperature of 70° C. to the outlet temperature of 80° C.

D) Preparation of Negative Electrode

A negative electrode slurry was prepared by mixing 90 wt. % hard carbon(HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),5 wt. % carbon black and 5 wt. % polyacrylonitrile in deionized water toform a slurry having a solid content of 50 wt. %. The slurry was coatedonto both sides of a copper foil having a thickness of 9 μm using atransfer coater with an area density of about 15 mg/cm². The coatedfilms on the copper foil were dried at about 50° C. for 2.4 minute by a24-meter-long conveyor hot air dryer operated at a conveyor speed ofabout 10 meter/minute to obtain a negative electrode.

Example 14 Assembling of Pouch-Type Battery

A pouch cell was prepared in the same manner as in Example 2.

Electrochemical Measurements of Example 14

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.7 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 9.

Example 15

A pouch cell was prepared in the same manner as in Examples 1 and 2,except that cathode material LiNi_(0.8)Mn_(0.1)Co_(0.1)O₂ (NMC811)(obtained from Henan Kelong NewEnergy Co., Ltd., Xinxiang, China) wasused instead of NMC333, and additive was not added. A positive electrodeslurry was prepared by mixing 91 wt. % pre-treated active batteryelectrode material, 5 wt. % carbon black (SuperP; Timcal Ltd, Bodio,Switzerland), and 4 wt. % polyacrylonitrile (PAN) (LA 132, ChengduIndigo Power Sources Co., Ltd., China) in deionized water to form aslurry having a solid content of 55 wt. %. The slurry was homogenized bya planetary stirring mixer (200 L mixer, Chienemei Industry Co. Ltd.,China) for 6 hours operated at a stirring speed of 20 rpm and adispersing speed of 1500 rpm to obtain a homogenized slurry. Theformulation of Example 15 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 12.7 Ah. Test result of cyclability performance is shown in Table2 below and FIG. 10.

Example 16

A pouch cell was prepared in the same manner as in Examples 1 and 2,except that cathode material LiNi_(0.6)Mn_(0.2)Co_(0.2)O₂ (NMC622)(obtained from Hunan Rui Xiang New Material Co., Ltd., Changsha, China)was used instead of NMC333, and additive was not added. A positiveelectrode slurry was prepared by mixing 90 wt. % pre-treated activebattery electrode material, 5 wt. % carbon black (SuperP; Timcal Ltd,Bodio, Switzerland), and 5 wt. % polyacrylonitrile (PAN) (LA 132,Chengdu Indigo Power Sources Co., Ltd., China) in deionized water toform a slurry having a solid content of 60 wt. %. The slurry washomogenized by a planetary stirring mixer (200 L mixer, ChienemeiIndustry Co. Ltd., China) for 6 hours operated at a stirring speed of 20rpm and a dispersing speed of 1500 rpm to obtain a homogenized slurry.The formulation of Example 16 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10 Ah. Test result of cyclability performance is shown in Table 2below and FIG. 11.

Example 17

A pouch cell was prepared in the same manner as in Examples 1 and 2,except that cathode material Li_(1.0)Ni_(0.8)Co_(0.15)Al_(0.05)O₂ (NCA)(obtained from Hunan Rui Xiang New Material Co., Ltd., Changsha, China)was used instead of NMC333, and additive was not added. A positiveelectrode slurry was prepared by mixing 91 wt. % pre-treated activebattery electrode material, 5 wt. % carbon black (SuperP; Timcal Ltd,Bodio, Switzerland), and 4 wt. % polyacrylonitrile (PAN) (LA 132,Chengdu Indigo Power Sources Co., Ltd., China) in deionized water toform a slurry having a solid content of 55 wt. %. The slurry washomogenized by a planetary stirring mixer (200 L mixer, ChienemeiIndustry Co. Ltd., China) for 6 hours operated at a stirring speed of 20rpm and a dispersing speed of 1500 rpm to obtain a homogenized slurry.The formulation of Example 17 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10 Ah. Test result of cyclability performance is shown in Table 2below and FIG. 12.

Example 18

A pouch cell was prepared in the same manner as in Examples 13 and 14,except that cathode material LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂ (NMC532)(obtained from Hunan Rui Xiang New Material Co. Ltd., Changsha, China)was used instead of LiCoO₂; alginic acid sodium salt (sodium alginate,obtained from Aladdin Industries Corporation, China) andpolyacrylonitrile were used instead of polyacrylonitrile as a cathodebinder material; and additive was not added. A positive electrode slurrywas prepared by mixing 88 wt. % pre-treated active battery electrodematerial, 6 wt. % carbon black (SuperP; Timcal Ltd, Bodio, Switzerland),2.5 wt. % alginic acid sodium salt, and 3.5 wt. % polyacrylonitrile (LA132, Chengdu Indigo Power Sources Co., Ltd., China) in deionized waterto form a slurry having a solid content of 50 wt. %. The slurry washomogenized by a planetary stirring mixer (200 L mixer, ChienemeiIndustry Co. Ltd., China) for 6 hours operated at a stirring speed of 20rpm and a dispersing speed of 1500 rpm to obtain a homogenized slurry.The formulation of Example 18 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.7 Ah. Test result of cyclability performance is shown in Table2 below and FIG. 13.

Comparative Example 1

A pouch cell was prepared in the same manner as in Examples 13 and 14,except that 1.5 wt. % carboxymethyl cellulose (CMC, BSH-12, DKS Co.Ltd., Japan) and 3.5 wt. % SBR (AL-2001, NIPPON A&L INC., Japan) wereused instead of 5 wt. % polyacrylonitrile as a cathode binder material,and 0.01 wt. % solution of acetic acid in water was used instead of amixture of H₂O and ethanol when pre-treating the cathode material. Aparticulate cathode material LiCoO₂ (obtained from Xiamen Tungsten CO.Ltd., China) was added to a stirring 0.01 wt. % solution of acetic acidin water (obtained from Aladdin Industries Corporation, China) at roomtemperature to form a suspension having a solid content of about 2% byweight. The pH of the suspension was measured using a pH meter and thepH was about 3.4. The suspension was further stirred at room temperaturefor 1 hour. Then the suspension was separated and dried by a 2.45 GHzmicrowave dryer (ZY-4HO, obtained from Zhiya Industrial MicrowaveEquipment Co., Ltd., Guangdong, China) at 750 W for 5 minutes to obtaina pre-treated active battery electrode material. A positive electrodeslurry was prepared by mixing 90 wt. % pre-treated active batteryelectrode material, 5 wt. % carbon black, 1.5 wt. % carboxymethylcellulose and 3.5 wt. % SBR in deionized water to form a slurry having asolid content of 50 wt. %. The slurry was homogenized by a planetarystirring mixer (200 L mixer, Chienemei Industry Co. Ltd., China) for 6hours operated at a stirring speed of 30 rpm and a dispersing speed of1500 rpm to obtain a homogenized slurry. The formulation of ComparativeExample 1 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 9.1 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 14.

Comparative Example 2

A pouch cell was prepared in the same manner as in Comparative Example1, except that 2 wt. % carboxymethyl cellulose (CMC, BSH-12, DKS Co.Ltd., Japan) and 3 wt. % polyvinyl alcohol (PVA) (obtained from TheNippon Synthetic Chemical Industry Co., Ltd., Japan) were used insteadof 1.5 wt. % carboxymethyl cellulose and 3.5 wt. % SBR as a cathodebinder material. A positive electrode slurry was prepared by mixing 90wt. % pre-treated active battery electrode material, 5 wt. % carbonblack, 2 wt. % carboxymethyl cellulose and 3 wt. % PVA in deionizedwater to form a slurry having a solid content of 50 wt. %. The slurrywas homogenized by a planetary stirring mixer (200 L mixer, ChienemeiIndustry Co. Ltd., China) for 6 hours operated at a stirring speed of 30rpm and a dispersing speed of 1500 rpm to obtain a homogenized slurry.The formulation of Comparative Example 2 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 8.2 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 15.

Comparative Example 3

A pouch cell was prepared in the same manner as in Examples 13 and 14,except that ball mill was used instead of planetary mixer as ahomogenizer when preparing the positive electrode slurry, and 0.01 wt. %solution of acetic acid in water was used instead of a mixture of H₂Oand ethanol when pre-treating the cathode material. A particulatecathode material LiCoO₂ (obtained from Xiamen Tungsten CO. Ltd., China)was added to a stirring 0.01 wt. % solution of acetic acid in water(obtained from Aladdin Industries Corporation, China) at roomtemperature to form a suspension having a solid content of about 2% byweight. The pH of the suspension was measured using a pH meter and thepH was about 3.4. The suspension was further stirred at room temperaturefor 1 hour. Then the suspension was separated and dried by a 2.45 GHzmicrowave dryer (ZY-4HO, obtained from Zhiya Industrial MicrowaveEquipment Co., Ltd., Guangdong, China) at 750 W for 5 minutes to obtaina pre-treated active battery electrode material. A positive electrodeslurry was prepared by mixing 90 wt. % pre-treated active batteryelectrode material, 5 wt. % carbon black (SuperP; Timcal Ltd, Bodio,Switzerland), and 5 wt. % polyacrylonitrile (PAN) (LA 132, ChengduIndigo Power Sources Co., Ltd., China) in deionized water to form aslurry having a solid content of 50 wt. %. The slurry was homogenized ina 500 mL container in a planetary-type ball mill (Changsha MITRInstrument & Equipment Co. Ltd., China) with thirty (too many?)zirconium oxide (ZrO₂) balls (fifteen 5 mm and fifteen 15 mm) for 3hours operated at a rotation speed of 150 rpm and spinning speed of 250rpm to obtain a homogenized slurry. The formulation of ComparativeExample 3 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 9.9 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 16.

Comparative Example 4

A pouch cell was prepared in the same manner as in Comparative Example1, except that 5 wt. % polyacrylonitrile were used instead of 1.5 wt. %carboxymethyl cellulose and 3.5 wt. % SBR as a cathode binder material.The formulation of Comparative Example 4 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.1 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 17.

Comparative Example 5

A pouch cell was prepared in the same manner as in Example 15, exceptthat 0.01 wt. % solution of citric acid in water was used instead of amixture of H₂O and ethanol when pre-treating the cathode material. Aparticulate cathode material NMC811 was added to a stirring 0.01 wt. %solution of citric acid in water (obtained from Aladdin IndustriesCorporation, China) at room temperature to form a suspension having asolid content of about 2% by weight. The pH of the suspension wasmeasured using a pH meter and the pH was about 3.4. The suspension wasfurther stirred at room temperature for 1 hour. Then the suspension wasseparated and dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained fromZhiya Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750W for 5 minutes to obtain a pre-treated active battery electrodematerial. The formulation of Comparative Example 5 is shown in Table 1below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 11.4 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 18.

Comparative Example 6

A pouch cell was prepared in the same manner as in Example 15, exceptthat the cathode material was not pre-treated. The formulation ofComparative Example 6 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 12.5 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 19.

Comparative Example 7

A pouch cell was prepared in the same manner as in Example 11, exceptthat 0.01 wt. % solution of citric acid in water was used instead of amixture of H₂O and iso-propanol when pre-treating the cathode material.A particulate cathode material C-S LNMgO was added to a stirring 0.01wt. % solution of citric acid in water (obtained from Aladdin IndustriesCorporation, China) at room temperature to form a suspension having asolid content of about 2% by weight. The pH of the suspension wasmeasured using a pH meter and the pH was about 3.6. The suspension wasfurther stirred at room temperature for 1 hour. Then the suspension wasseparated and dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained fromZhiya Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750W for 5 minutes to obtain a pre-treated active battery electrodematerial. The formulation of Comparative Example 7 is shown in Table 1below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 20.

Comparative Example 8

A pouch cell was prepared in the same manner as in Example 13, exceptthat 1.5 wt. % carboxymethyl cellulose (CMC, BSH-12, DKS Co. Ltd.,Japan) and 3.5 wt. % SBR (AL-2001, NIPPON A&L INC., Japan) were usedinstead of 5 wt. % polyacrylonitrile as an anode binder material. Theformulation of Comparative Example 8 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 11.2 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 21.

Comparative Example 9

A pouch cell was prepared in the same manner as in Example 13, exceptthat 5 wt. % polyvinylidene fluoride (PVDF; Solef® 5130, obtained fromSolvay S.A., Belgium) was used instead of 5 wt. % polyacrylonitrile asan anode binder material; and N-methyl-2-pyrrolidone (NMP; purity of≧99%, Sigma-Aldrich, USA) was used instead of deionized water as asolvent. A negative electrode slurry was prepared by mixing 90 wt. %hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,Guangdong, China), 5 wt. % carbon black and 5 wt. % PVDF in NMP to forma slurry having a solid content of 50 wt. %. The slurry was coated ontoboth sides of a copper foil having a thickness of 9 μm using a transfercoater with an area density of about 15 mg/cm². The coated films on thecopper foil were dried at about 87° C. for 8 minute by a 24-meter-longconveyor hot air dryer operated at a conveyor speed of about 3meter/minute to obtain a negative electrode. The formulation ofComparative Example 9 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.4 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 22.

Comparative Example 10

A pouch cell was prepared in the same manner as in Example 13, exceptthat a vacuum oven (HSZK-6050, Shanghai Hasuc Instrument ManufactureCo., Ltd., China) was used instead of a microwave dryer for drying thepre-treated cathode material. The pre-treated cathode material was driedin a vacuum oven at 88° C. for 8 hours. The formulation of ComparativeExample 10 is shown in Table 1 below.

The cell was tested galvanostatically at a current density of C/2 at 25°C. on a battery tester between 3.0 V and 4.2 V. The nominal capacity wasabout 10.3 Ah.

The cyclability performance of the pouch cell was tested by charging anddischarging at a constant current rate of 1 C between 3.0 V and 4.2 V.Test result of cyclability performance is shown in Table 2 below andFIG. 23.

TABLE 1 Cathode Pre- Cathode slurry Anode slurry Example materialtreatment Binder Solvent Homogenizer Binder Solvent Example 1 NMC333H₂O/ PAN H₂O Planetary PAN H₂O ethanol mixer Example 3 LMO Acetic PANH₂O Ultrasonic PAN H₂O acid flow cell Example 5 NMC333 H₂O PAN H₂OUltrasonic PAN H₂O flow cell Example 7 LiFePO₄ Acetic PAN H₂O UltrasonicPAN H₂O acid flow cell Example 9 C—S NMC532 H₂O/ PAN H₂O Planetary PANH₂O methanol mixer Example 11 C—S LNMgO H₂O/iso- PAN H₂O Planetary PANH₂O propanol mixer Example 13 LiCoO₂ H₂O/ PAN H₂O Planetary PAN H₂Oethanol mixer Example 15 NMC811 H₂O/ PAN H₂O Planetary PAN H₂O ethanolmixer Example 16 NMC622 H₂O/ PAN H₂O Planetary PAN H₂O ethanol mixerExample 17 NCA H₂O/ PAN H₂O Planetary PAN H₂O ethanol mixer Example 18NMC532 H₂O/ Alginic H₂O Planetary PAN H₂O ethanol acid + mixer PANComparative LiCoO₂ Acetic CMC + H₂O Planetary PAN H₂O Example 1 acid SBRmixer Comparative LiCoO₂ Acetic CMC + H₂O Planetary PAN H₂O Example 2acid PVA mixer Comparative LiCoO₂ Acetic PAN H₂O Ball mill PAN H₂OExample 3 acid Comparative LiCoO₂ Acetic PAN H₂O Planetary PAN H₂OExample 4 acid mixer Comparative NMC811 Citric PAN H₂O Planetary PAN H₂OExample 5 acid mixer Comparative NMC811 / PAN H₂O Planetary PAN H₂OExample 6 mixer Comparative C—S LNMgO Citric PAN H₂O Planetary PAN H₂OExample 7 acid mixer Comparative LiCoO₂ H₂O/ PAN H₂O Planetary CMC + H₂OExample 8 ethanol mixer SBR Comparative LiCoO₂ H₂O/ PAN H₂O PlanetaryPVDF NMP Example 9 ethanol mixer ¹Comparative LiCoO₂ H₂O/ PAN H₂OPlanetary PAN H₂O Example 10 ethanol mixer Note: ¹The pre-treatedcathode material was dried in a vacuum oven.

The cyclability performance of the pouch cells of Examples 1-18 andComparative Examples 1-10 was tested by charging and discharging at aconstant current rate of 1 C. The capacity retentions of the cells weremeasured during cycling and estimated by extrapolation based on theplotted results. The measured and estimated values are shown in Table 2below.

TABLE 2 Estimated values Measured values by extrapolation CapacityCapacity Example No. of Cycle retention (%) No. of Cycle retention (%)Example 2 450 95.6 2,000 80.4 Example 4 2,000 77   / / Example 6 56094.8 2,000 81.4 Example 8 3,000 82.6 / / Example 10 361 98.6 2,000 92.2Example 12 385 98.1 2,000 90.1 Example 14 576 94.4 2,000 80.6 Example 15476 95.7 2,000 81.9 Example 16 497 94.4 2,000 77.5 Example 17 553 93.92,000 77.9 Example 18 522 93.1 2,000 73.6 Comparative 85 78.7 / /Example 1 Comparative 113 70.4 / / Example 2 Comparative 506 92.1 200070.0 Example 3 Comparative 514 93.4 2,000 74.3 Example 4 Comparative 46690.1 2,000 57.5 Example 5 Comparative 485 93.8 2,000 74.4 Example 6Comparative 413 92.6 2,000 64.2 Example 7 Comparative 508 95.1 2,00080.7 Example 8 Comparative 606 94.3 2,000 81.2 Example 9 Comparative 47294.8 2,000 78.0 Example 10

The comparison battery cells had a discharge capacity retention lessthan 80% after only less than 100 cycles when water-soluble binders suchas CMC, SBR and PVA were used for preparing the aqueous slurry. Incontrast, the batteries of Examples 1-18 had a discharge capacityretention of at least 86% after 1000 cycles.

This excellent cyclability indicates that battery cell made of cathodeand anode electrodes prepared by the method disclosed herein can achievecomparable or even better stability compared to battery cell made ofcathode and anode electrodes prepared by conventional method involvingthe use of organic solvents.

While the invention has been described with respect to a limited numberof embodiments, the specific features of one embodiment should not beattributed to other embodiments of the invention. In some embodiments,the methods may include numerous steps not mentioned herein. In otherembodiments, the methods do not include, or are substantially free of,any steps not enumerated herein. Variations and modifications from thedescribed embodiments exist. The appended claims intend to cover allthose modifications and variations as falling within the scope of theinvention.

1. A method of preparing a battery electrode, comprising the stepsof: 1) pre-treating a cathode material in a first aqueous solutionhaving a pH from about 7.0 to about 8.0 to form a first suspension; 2)drying the first suspension to obtain a pre-treated cathode material; 3)dispersing the pre-treated cathode material, a conductive agent, and abinder material in a second aqueous solution to form a slurry; 4)homogenizing the slurry by a homogenizer to obtain a homogenized slurry;5) applying the homogenized slurry on a current collector to form acoated film on the current collector; and 6) drying the coated film onthe current collector to form the battery electrode; wherein the firstaqueous solution is water, alcohol, or a mixture of water and alcohol;and wherein the cathode material is a lithium transition metal oxide ora core-shell composite comprising a core comprising a lithium transitionmetal oxide and a shell formed by coating the surface of the core with atransition metal oxide or lithium transition metal oxide; wherein eachof the lithium transition metal oxides is independently selected fromthe group consisting of LiCoO₂, LiNiO₂, LiNi_(x)Mn_(y)O₂,Li_(1+z)Ni_(x)Mn_(y)Co_(1-x-y)O₂, LiNi_(x)Co_(y)Al_(z)O₂, LiV₂O₅,LiTiS₂, LiMoS₂, LiMnO₂, LiCrO₂, LiMn₂O₄, LiFeO₂, LiFePO₄, andcombinations thereof; wherein each x is independently from 0.3 to 0.8;each y is independently from 0.1 to 0.45; and each z is independentlyfrom 0 to 0.2; and wherein the transition metal oxide is selected fromthe group consisting of Fe₂O₃, MnO₂, Al₂O₃, MgO, ZnO, TiO₂, La₂O₃, CeO₂,SnO₂, ZrO₂, RuO₂, and combinations thereof.
 2. The method of claim 1,wherein the cathode material is a nickel-rich cathode material selectedfrom NMC532, NMC622, NMC811, or Li_(1.0)Ni_(0.8)Co_(0.15)Al_(0.05)O₂. 3.The method of claim 1, wherein the first suspension is stirred for atime period from about 2 minutes to about 12 hours.
 4. The method ofclaim 1, wherein the first aqueous solution is alcohol or a mixture ofwater and alcohol and wherein the alcohol is selected from ethanol,isopropanol, methanol, n propanol, t-butanol, or a combination thereof.5. The method of claim 1, wherein the first suspension is dried by adouble-cone vacuum dryer, a microwave dryer, or a microwave vacuumdryer.
 6. The method of claim 1, wherein the conductive agent isselected from the group consisting of carbon, carbon black, graphite,expanded graphite, graphene, graphene nanoplatelets, carbon fibres,carbon nano-fibers, graphitized carbon flake, carbon tubes, carbonnanotubes, activated carbon, mesoporous carbon, and combinationsthereof.
 7. The method of claim 1, wherein the conductive agent ispre-treated in a basic solution for a time period from about 30 minutesto about 2 hours and wherein the basic solution comprises a baseselected from the group consisting of H₂O₂, LiOH, NaOH, KOH, NH₃.H₂O,Be(OH)₂, Mg(OH)₂, Ca(OH)₂, Li₂CO₃, Na₂CO₃, NaHCO₃, K₂CO₃, KHCO₃, andcombinations thereof.
 8. The method of claim 1, wherein the conductiveagent is dispersed in a third aqueous solution to form a secondsuspension prior to step 3).
 9. The method of claim 1, wherein thebinder material is selected from the group consisting ofstyrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC),polyvinylidene fluoride (PVDF), acrylonitrile copolymer, polyacrylicacid (PAA), polyacrylonitrile, poly(vinylidenefluoride)-hexafluoropropene (PVDF-HFP), latex, a salt of alginic acid,and combinations thereof.
 10. The method of claim 9, wherein the bindermaterial is the salt of alginic acid and wherein the salt of alginicacid comprises a cation selected from Na, Li, K, Ca, NH₄, Mg, Al, or acombination thereof.
 11. The method of claim 8, wherein the bindermaterial is dissolved in a fourth aqueous solution to form a resultingsolution prior to step 3).
 12. The method of claim 11, wherein each ofthe first, the second, third and fourth aqueous solutions independentlyis purified water, pure water, de-ionized water, distilled water, or acombination thereof.
 13. The method of claim 1, wherein the homogenizeris a stirring mixer, a planetary stirring mixer, a blender, a mill, anultrasonicator, a rotor-stator homogenizer, or a homogenizer.
 14. Themethod of claim 13, wherein the ultrasonicator is a probe-typeultrasonicator or an ultrasonic flow cell.
 15. The method of claim 1,wherein the homogenized slurry is applied on the current collector usinga doctor blade coater, a slot-die coater, a transfer coater, or a spraycoater.
 16. The method of claim 1, wherein the coated film is dried fora time period from about 1 minute to about 30 minutes at a temperaturefrom about 45° C. to about 100° C.
 17. The method of claim 1, whereinthe cathode material is the core-shell composite comprising the corecomprising the lithium transition metal oxide and the shell formed bycoating the surface of the core with the lithium transition metal oxide,and wherein each of the lithium transition metal oxides in the core andthe shell is independently doped with a dopant selected from the groupconsisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge,and combinations thereof.
 18. The method of claim 1, wherein the cathodematerial is the core-shell composite, and wherein the diameter of thecore is from about 5 μm to about 45 μm and the thickness of the shell isfrom about 3 μm to about 15 μm
 19. The method of claim 1, wherein theelectrode is able to retain at least about 83% of its initial storagecapacity after 1,000 cycles at a rate of 1 C at room temperature in afull cell.